1. Field of the Invention
The present invention relates to a position/posture measurement device for measuring positions and postures of a plurality of articles, and a robot system including the position/posture measurement device and a robot for carrying out an operation with respect to the articles.
2. Description of the Related Art
In a robot system for carrying out an operation such as taking out by using a robot with respect to a plurality of articles positioned within a predetermined region such as a container or pallet, the position and posture (hereinafter, also referred to as “position/posture”) of the article are measured before the operation. In the prior art, various methods or devices have been proposed for measuring the position/posture of the articles to be operated.
For example, JP 2010-210511 A discloses a three-dimensional position/posture recognition device, in which an object is recognized by comparing three-dimensional position/posture data of a group of the objects and three-dimensional position/posture model data of the object after changing the position/posture of the object, and by determining the object having a high degree of coincidence with the position/posture of the three-dimensional model thereof.
JP 2009-128191 A discloses an article recognition device, in which an object is positioned with high speed based on a feature of the object such as a spin image, a three-dimensional feature data (model) of the object are compared to a distance data (scene) obtained by a range sensor, and the three-dimensional position/posture of the object are rapidly recognized. This document describes that, by using position/posture information output from the article recognition device, a robot can be rapidly operated based on the actual position/posture of the object.
For example, in case that a plurality of articles having the same shape is randomly located while contacting or overlapping with each other, when the position/posture of each article should be measured by comparing the three-dimensional model and the measurement data, the same feature of the article may be repeatedly observed within a measurement region, whereby a measurement error may be generated (refer to FIG. 5 and an explanation thereof as described below). Such a measurement error may be generated due to a positional relationship between the articles, and is difficult to be solved by the technique for improving measurement accuracy of each article, as described in JP 2010-210511 A or JP 2009-128191 A. As a result, it is difficult to properly take out the article by using the robot based on the measurement result.